adding env var

Author: Bogdan Abaev

server/Dockerfile

@@ -4,5 +4,5 @@ COPY package*.json ./
 RUN npm install
 COPY . .
 EXPOSE 3000
-ENV DB_URL='54.237.77.73:27017'
+ENV DB_URL="mongodb://54.237.77.73:27017"
 CMD [ "npm", "start" ]